Oil and gas wells are ordinarily completed by first cementing metallic casing stringers in the borehole. During the drilling, completion, and production phase, operators often find it useful to perform various remedial work, repair, or other maintenance in the casing string. For example, it is sometimes useful to cut and remove a section of a tubing string or well casing. During a typical cutting operation, it is generally desirable to stabilize the cutting tool so as to improve the efficiency of the cutting operation. Those of ordinary skill in the art will readily appreciate that improved efficiency results in a reduction of time and therefore a cost savings.
Numerous stabilizing and/or centralizing mechanisms are known in the art for use in downhole operations including drilling and workover operations. Such stabilizing mechanisms include, for example, mechanically and hydraulically actuated toggle mechanisms, spring actuated mechanisms, hydraulically actuated cam-driven or cone-driven mechanisms, hydraulically actuated piston mechanisms, as well as standard fixed blade stabilizing mechanisms. While various stabilizing mechanisms have been widely used in downhole operations, they are often not well suited for certain casing cutting operations.
For example, toggle mechanisms do not provide consistent stabilizing force. Toggle mechanisms are also prone to failure in service. Spring mechanisms are not well suited for cutting operations in that they tend to allow radial movement of the stabilized assembly which can negate (or partially negate) the stabilization. Radial piston assemblies, while capable of providing a suitable stabilizing force, are prone to catastrophic seal failure and tend to have geometric constraints. Moreover, piston mechanisms can damage the casing owing to the application of too much radial force. Cam-driven and cone-driven mechanisms also tend to be limited by geometric constraints, in particular by the amount of radial stroke that can be generated within a downhole assembly. Fixed blade (passive) stabilizers, commonly utilized in drilling operations, allow the axial translation, but do not generally provide adequate radial stabilization, especially as the blades wear over time. In particular, passive stabilizers have a built-in radial clearance that wears with time and allows for radial movement (and therefore vibration and oscillation that tends to reduce cutting efficiency and damage cutting tools). Hydraulic stabilization mechanisms may provide suitable radial stabilization but tend to have excessive clamping forces that do not allow for axial translation of the cutting tool during the cutting operation.